Terpenes and terpenoids represent a large complex class of compounds built upon the isoprene unit, C5H8. Some terpenes and terpenoids have been used in the food, flavor and fragrance industries. Typically they are of plant or microbial origin and are often bound to tannins or glycosides.
Terpenes, which are important contributors to many fruit and floral scents, are synthesized from geranyl diphosphate (GDP), an intermediate in carotenoid biosynthesis. Monoterpene perillyl alcohol has been reported to inhibit photocarcinogenesis in a non-melanoma model of mouse skin carcinogenesis and UVB-induced skin carcinogenesis. Perillyl alcohol caused a reduction in UVB-induced non-melanoma tumors (Barthelman et al., Cancer Res. 58:711-716, 1998). Topical pretreatment but not post-treatment of the melanoma cells with perillyl alcohol markedly reduced levels of UV-induced reactive oxygen species. These studies suggest that perillyl alcohol inhibits the Ras signaling pathway and thus can be an effective target for chemoprevention of melanoma (Lluria-Prevatt et al., Cancer Epidemiology, Biomarkers & Prevention, 11(6):573-579, 2002).
Numerous studies have shown major changes in gene expression patterns associated with terpene exposure (Nakamura et al., FEBS Letters, 572(1-3): 245-250, 2004; Einbond et al., Anticancer Research, 27(2):697-712, 2007; Rahman et al., Cancer Research, 66(9):4952-4960, 2006). Very frequently gene expression changes involve clusters of genes directly or indirectly involved in lowering rates of cell proliferation, increasing antioxidative enzymes and increasing apoptosis. Some terpenes can act directly on epithelial cells in vitro and produce many of the same responses seen in vivo (Kim et al., Molecular Cancer Therapeutics, 1(3):177-184, 2002). Some triterpenes exhibited cancer preventative capacity in breast, uterus, and lung cancer, respectively (Niwa et al., Oncology Reports, 17(3): 617-622, 2007; Liby et al., Cancer Research, 67(6): 2414-2419, 2007). Extract of a plant Rabdosia rubescens was reported to prevent cancer due to its content of diterpenoids (Ho et al., U.S. Pat. No. 7,351,739, 2008). Another plant extract from Acacia victoriae containing saponins suggested that it is the triterpenes which exhibited exhibit potent anti-tumor effects against a variety of tumor cells (Arntzen et al., US Patent Publication US2006/0073222 A1).
Kunsch et al., U.S. Pat. No. 7,247,714 suggests that certain compounds can activate cytoprotective response elements (CPREs) that have been identified to induce, coordinate and activate certain genes that protect cells from the potentially damaging effects of oxidative stress. CPREs have the DNA consensus sequence 5′-RTGACWNAGCANW-3′, wherein R=A or G, W=A or T, and N=A, G, C or T. The cellular functions of CPRE regulated genes are diverse, however in general, these genes act in various capacities to regulate and maintain redox homeostasis in the cell. The CPRE is unique, and different from the antioxidant response element (ARE) and the maf-recognition element (MARE).
d-Limonene is a cyclic monoterpene that can serve as a precursor to a host of other oxygenated monocyclic monoterpenes such as carveol, carvone, menthol, perillyl alcohol and perillaldehyde. It is characterized as a non-nutritive dietary component. d-Limonene is found in the essential oils of citrus fruits, cherry, mint and herbs. It is widely used in foods, flavors, fragrances, house hold products and skin cleansing formulation. d-Limonene is metabolized to oxygenated metabolites in rats and in humans. In rats, the two major serum metabolites of d-limonene are perillic acid and dihydroperillic acid. d-Limonene and its metabolites are detectable in serum, liver, lung and many other tissues with higher concentrations detected in adipose tissue and mammary gland than in less fatty tissues (Crowell et al., Cancer Chemother. Pharmacol. 31:205-212, 1992). Humans produce these two serum metabolites as well as limonene-1,2-diol (Crowell et al., Cancer Chemother. Pharmacol. 35:31-37, 1994). Metabolism of perillyl alcohol and d-limonene are similar.
Nootkatone is a sesquiterpene, present in grapefruit, tangerine, orange juices and oils. It does not appear to be toxic, at least at the concentrations found in normal strength grapefruit juice (approximately 0.0035%, or 35 ppm).
Norisoprenoid beta-damascenone is a widely used fragrance and flavor material present in a wide variety vegetables and teas. It is found also in grapes and wine either glycosylated or as an aglycon. Between 1 and 10 metric tons are used annually in the flavor and fragrance industry. No phototoxicity or photoallergenity has been reported in humans after topical application of beta-damascenone and UV-radiation. No skin irritation was observed in mice, guinea pigs and humans up to 5%. Higher concentration than 5% has not been tested. The LD50 was reported to be greater than 2.0 g/kg (Lapczynski et al., Food and Chemical Toxicology, 45(1): S172-S178, 2007).
Natural and synthetic vitamin A derivatives (retinoids) have been used extensively in the treatment of a variety of skin disorders and have been used as skin repair or renewal agents. Vitamin A is a diterpenoid. Compounds such as retinol occur naturally in the human body and are essential for normal epithelial cell differentiation. Retinoic acid, for example, has been used to treat a variety of skin conditions such as, for instance, acne, wrinkles, psoriasis, age spots and discoloration (Rollman and Vahlquist, Arch Dermatol Res., 278(1):17-24, 1985a, and Rollman and Vahlquist, Br J. Dermatol., 113(4): 405-413, 1985b; Lowe and David, Pharmacol Skin 3:240-248, 1989). Although retinoids efficiently arrest the cell cycle of many types of epithelial tumors during the G1 stage, no single common mechanism of action has been identified. Retinal (preformed vitamin A) and/or certain carotenoids (provitamin A) are converted to retinol in the body, as needed. Retinol and the other retinoids are integrally involved in cell growth and differentiation, which may affect carcinogenesis.
Vitamin C (L-ascorbic acid) has been described for use in topical administration to reinforce the cohesion of the dermo-epidermal junction (Bernerd, F. U.S. patent application Ser. No. 10/358,888, 2003). Pharmacologically, ascorbate ion is an antioxidant which is required as cofactor in collagen synthesis. Some studies suggested that ingestion of vitamin C rejuvenates skin. The same was observed with omega-6-linolenic acid.
The epidermal cornified cell envelope is a complex protein-lipid composite that replaces the plasma membrane of terminally differentiated keratinocytes and is different than the stratum corneum, which is the external protective layer on the skin surface. The cornified envelope is a precursor structure for the corneum and has the ability to prevent the loss of water and ions and to protect from environmental hazards similar to that of the corneum. The major protein of the cornified cell envelope of the terminally differentiated keratinocytes is loricrin which is eventually crosslinked to the keratin of the corneum. Loricrin contributes about 70% to the protein mass of the envelope cells, but is a minor percentage of the protein mass of the corneum (Candi et al., Nature Reviews Molecular Cell Biology 6:328-340, 2005).
Its gene expression is limited to human keratinocytes of stratified squamous epithelia. A VEGF, or vascular endothelial growth factor, that represents in the skin a major angiogenesis factor, is downregulated after UV-light exposure. Matrix metalloproteinases (MMPs) are enzymes that degrade the extracellular matrix in the context of physiological remodeling of the skin, but age and exposure to UV radiation have the effect of increasing the activity of these MMPs, in particular that of MMP1, MMP3 and MIMP9.
UVR causes skin inflammation and redness (erythema) associated with sunburn. Sunscreen products typically applied in the form of a cream consist of active ingredients that adsorb UV-rays directly. Suitable sunscreens can have UVA absorbing properties, UVB absorbing properties or a mixture thereof. The exact amount of the sunscreen active may vary depending upon the desired Sun Protection Factor, i.e. the “SPF” of the composition as well as the desired level of UVA protection. SPF is a commonly used measure of photoprotection of a sunscreen against erythema. The SPF is defined as a ratio of the ultraviolet energy required to produce minimal erythema on protected skin to that required to produce the same minimal erythema on unprotected skin in the same individual (See, Federal Register, 43(166): 38206-38269, Aug. 25, 1978). Suitable sunscreens include, but are not limited to, those found in the CTFA International Cosmetic Ingredient Dictionary and Handbook, 7th edition, volume 2 pp. 1672, edited by Wenninger and McEwen (The Cosmetic, Toiletry, and Fragrance Association, Inc., Washington, D.C., 1997).
Suitable UVA absorbing sunscreen actives include, for instance, dibenzoylmethane derivatives, anthranilate derivatives such as methylanthranilate and homomethyl, 1-N-acetylanthranilate, and mixtures thereof. Examples of dibenzoylmethane sunscreen actives are described in U.S. Pat. No. 4,387,089 issued to Depolo; and in Sunscreens: Development, Evaluation, and Regulatory Aspects edited by N. J. Lowe and N. A. Shaath, Marcel Dekker, Inc (1990). These are all UVR absorbing type of sunscreen providing broad-spectrum UVA protection either independently, or in combination with, other UV protective actives that may be present in the composition.
Terpenes display some very interesting properties related to cancer prevention (Morita et al., Immunological Reviews 215: 59-76, 2007; Liby et al., Cancer Research, 67(6): 2414-2419, 2007; Niwa et al., Oncology Reports, 17(3): 617-622, 2007; Sengottuvelan et al., Carcinogenesis, 27(5): 1038-1046, 2006). Their relative safety makes them suitable for use in flavors and fragrances. Sometimes stereo-isomers of the same terpene have entirely different sensory profiles. Carvone is an example: 4R-(−)-carvone exhibits sweet spearmint flavor, whereas 4S-(+)-carvone tastes like caraway. Terpenes also tend to exhibit relatively high hydrophobicity and some are perceived as bitter to humans. Hydrophobicity allows terpenes to interact directly with cell membranes to trigger responses, such as greater level of anti-oxidation and apoptosis. Terpenes such as limonene, farnesol, geraniol and nerolidol have been suggested for transdermal and transmucosal drug delivery (e.g. Aqil et al., Drug Discovery Today 12(23-24):1061-1067, 2007). The penetration of terpenes is linked to their size, hydrophobicity, chirality, saturation and boiling point.
It seems that the receptor sites for bitter substances on the taste cells tends to be hydrophobic (Katsuragi et al., Biochim Biophys Acta 1289:322-328, 1996) and may provide a mechanism whereby terpenes can interact directly with cell membranes to trigger responses, such as greater levels of anti-oxidation and apoptosis. Two additional important characteristics of terpene flavors are intensity and threshold concentration which are determined by the specificity of receptors (Ruiz et al., Chemical Senses 31(9):813-820, 2006). Terpenes are useful as skin penetration enhancers and agents involved in the prevention and therapy of inflammatory diseases. Some terpenes are better at preventing cancer than others and some can extend lifespan in addition to preventing cancer. Activity generally tends to increase with the order of polyterpenes and also hydroxylation (Crowell et al., Carcinogenesis 13(7):1261-1264, 1992). Because of variable tastes and taste intensities and documented utility as dietary inhibitors of carcinogenesis, the huge variety of available terpenes provides a fertile field for establishing how they might be useful in sunburn protection and cancer prevention (Dragsted et al., Pharmacology & Toxicology 1:116-135, 1993; Craig, American J. Clinical Nutrition 70(3): 491-499, 1999; Ray, Indian J. Cancer, 42(1):15-24, 2005). Several terpenes have been established as cancer prevention agents in mice. Initiation of breast cancer induced by ionizing radiation or DMBA in rats was almost completely prevented by the monoterpene d-limonene and its hydroxylated derivative, perillyl alcohol, without any evidence of toxicity, and both agents were effective therapeutically as well (Crowell et al., Carcinogenesis 13(7): 1261-1264, 1992; Gould, J. Cell. Biochem. 22:139-144, 1995. Geraniol was about 5-fold more effective than perillyl alcohol against the growth of human transplanted pancreatic adenocarcinomas (Burke et al., Lipids 32(2):151-156, 1997).
A triterpene, actein, exhibited a synergistic therapeutic effect with 5-fluorouracil (a cancer chemotherapeutic agent) against human breast cancer cells in vitro apparently by causing increased apoptosis (Einbond et al., Planta Medica 72(13):1200-1206, 2006). The synthetic triterpene 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid (CDDO) at nanomolar concentrations exhibited potent antiproliferative, pro-differentiation, and anti-inflammatory activities and large increases in the cytoprotective heme oxygenase-1 (HO-1) enzyme in vitro and in vivo. A similar inhibition of mouse lung tumors was noted based on anti-oxidative activity. (Liby et al., Cancer Research 65(11): 4789-4798, 2005; Liby et al., Cancer Research 67(6): 2414-2419, 2007). Mechanistic studies have found that triterpenes are strongly pro-apoptotic for human small cell lung cancer cells in vitro and act by blocking NF-KappaB thereby elevating apoptosis (Shishodia et al., Clinical Canc. Res. 12(6):1828-1838, 2006; Kim et al., Molecular Cancer Therapeutics 1(3): 177-184, 2002).
Numerous studies have shown major changes in gene expression patterns associated with terpene exposure (Nakamura et al., FEBS Letters 572(1-3): 245-250, 2004; Einbond et al., Anticancer Research 27(2):697-712, 2007; Gould, M. N. Enciron. Health Perspectives 105: Suppl, 977-979 1997; Rahman et al., Cancer Research 66(9): 4952-4960, 2006). Very frequently gene expression changes involve clusters of genes directly or indirectly involved in lowering rates of cell proliferation, increasing antioxidative enzymes and increasing apoptosis; all of which tend to block neoplastic growth. Several key genes that recur often in these studies are survivin, NFKappaB, TRAF, bcl-2 and IAP-2 (Shishodia et al., Clin. Canc. Res. 12(6):1828-1838, 2006). Colon cancer induced in rats by 1,2-dimethylhydrazine was inhibited 67% (p<0.01) by 8 mg/kg of the phytoalexin, resveratrol (Sengottuvelan et al., Carcinogenesis 27(5):1038-1046, 2006). Other studies show that hydrophobic receptors may play a role in causing apoptosis of cancer cells. Hydrophobic statins induced apoptosis and/or growth arrest in HCT116 cells (Powell et al., Biochem. J. 356:481-486, 2001) and the cytotoxicity of various organic compounds against ovarian cancer cells was correlated with their hydrophobic and steric properties (Verma et al., 3(4):441-450, 2006).
Hypotheses proposed to explain the cancer preventive activity of terpenes are generally variations on 1) altered cell signaling through gene expression changes, 2) antioxidative activity and 3) pro-apoptosis effects (Niwa et al., Oncology Reports 17(3):617-622, 2007; Shishodia et al., 12(6):1828-1838, 2006; Einbond et al., Anticancer Research 27(2):697-712, 2007; Pusztai et al., Anticancer Research 27(1A):201-205, 2007; Duarte et al., Planta Medica 72(2):162-168, 2006). Monoterpenes are known to inhibit the isoprenylation of small G proteins which affects signal transduction and alters gene expression and can affect the cell cycle (Gould, Environ. Health Perpsectives 105: 977-979, 1997). Studies of mammary cancer show a series of effects including blockage of the G1 phase of the cell cycle, followed by apoptosis, redifferentiation, and frequently complete tumor regression (Gould, Environ. Health Perpsectives 105: 977-979, 1997; Crowell, P. L. J. Nutrition 129(3):775-778, 1999). The theme that terpenes can activate apoptosis and can have antioxidative and anti inflammatory activity is recurrent in the literature (Ray, Indian Journal of Cancer 42(1):15-24, 2005; Wei et al., Carcinogenesis 14:1195-1201, 1993). For example, quercetin and omega-3-fatty acids in colorectal and prostate cancer responded to the terpene, lycopene (Lambert et al., Am. J. Clin. Nutr. 81(1):284-291, 2005. Others have found that the pyrophosphorylated isoprenoid intermediates and their metabolites are involved in the activation of the Vgamma2Vdelta2 T cells (Morita et al., Immun. Reviews 215:59-76, 2007), which enhances the removal of tumor cells because of better recognition by T-cells and natural killer receptors. Additionally, hydrophobicity and steric parameters of the terpenes may be one of the most important determinants of cytotoxic activity (Verma et al., Molec. Pharm. 3(4):441-450, 2006). Some synthetic triterpenes are strong inhibitors of inflammatory processes like induction of nitric oxide synthase (iNOS) and COX2 but also elevate phase 2 responses, including heme oxygenase 2 via the Nrf2-Keap1 signaling pathway (Dinkova-Kostova et al., PNAS 102(12):4584-4589, 2005).